1. Field of the Invention
The present invention relates generally to methods and devices for controlling the operation of moveable barrier operators. More specifically, the invention relates to determining the precise position of a moveable barrier relative to the fully open position and fully closed position.
2. Background Art
Moveable barrier operators are automated systems which are utilized to move a barrier between a fully open position and a fully closed position. Some examples of moveable barriers are sliding gates, swing gates, and barrier arms. A typical moveable barrier operator consists of a motor coupled to a drive train attached to the moveable barrier to move the barrier between a fully closed position and a fully open position.
Prior systems have typically used a variety of physical mechanical stops, mechanical limit switches or magnetic sensors to determine the fully open or fully closed positions. Others have incorporated encoders to count the number of pulses between the fully open or fully closed positions or resistive potentiometers to determine positioning of the moveable barrier.
The limit switches and magnetic sensors provide an indication only if the moveable barrier is at the fully open or fully closed position. Any other position of the moveable barrier is indeterminate. An encoder may be accurate in determining the barrier position as long as the counter circuitry's power is not interrupted or the barrier is not mechanically released from the drive train. In such cases, true position is lost and indeterminate until the moveable barrier has been driven to either a fully open or fully closed position. Resistive potentiometers need to be coupled such that they are indicative of the pivot point of the moveable barrier and being an electromechanical device, they are susceptible and prone to failure due to wear from the device's wiper on the resistive element.